It has heretofore been proposed in U.S. Pat. No. 3,317,825 to Huff of May 2, 1967 and in U.S. Pat. No. 3,383,588 to Stoll of May 14, 1968 to provide a portable, three prong, circuit tester for electric sockets in which three lamps are triangularly arranged in side by side chambers.
In U.S. Pat. No. 2,598,775 to Fischer of June 3, 1952, a similar portable ground tester is disclosed in which the three test lamps are rectilinearly arranged in side by side relationship.